1. Field of the Invention
The present invention relates to a treating method for decomposing halogenated organic compounds such as chlorofluorocarbons (CFC group, for instance flon), trichloroethylene, methyl bromide, and halon by making the compounds contact with catalyst effectively. Further, the present invention relates to the catalyst used in the treating method for decomposing organohalogen compounds, a preparing method thereof, and treating apparatus for the decomposition.
2. Description of the Prior Art
Organohalogen compounds containing fluorine, chlorine, or bromine such as chlorofluorocarbons, trichloroethylene, methyl bromide, halon, and the like are widely used as foaming agents, refrigerants, fire extinguisher, fumigants, and the like. However, the above described organohalogen compounds cause destruction of the ozone layer, and have serious influences such as generation of carcinogens and the like to the environment.
Therefore, various treating methods for recovering and decomposing the organohalogen compounds have been investigated. As treating methods for decomposing organohalogen compounds, a method using catalyst, a method using combustion at high temperature such as 800.about.900.degree. C., a method using plasma, and others are well known. Among them, the methods using combustion and plasma consume a large amount of fuel, and electric power, and have low energy efficiencies. Further, these methods have a problem such that reactor walls are damaged by generated corrosive halogens. Especially, the method using plasma has a large amount of energy loss because a high temperature exceeding 6000.degree. C. is used. On the contrary, the method using catalyst is a superior method if the catalyst has a high activity because only a small amount of energy is required.
As for the method using catalyst, a method using catalyst containing titania was disclosed in JP-B-6-59388 (1994). A catalyst containing titania and tungsten oxide, and a catalyst containing titania and vanadium oxide are described in the reference. However, organohalogen compounds to be contacted with the above disclosed catalysts are restricted to the organohalogen compounds having only one carbon atom with no carbon-hydrogen bond in a gas flow state, and embodiments in the reference showed only a case for treating carbontetrachloride of ppm order. The catalyst containing titania and tungsten oxide is defined as TiO.sub.2 containing tungsten oxide as W metal by a content of about 0.1.about.20% by weight (if converted to atomic percentage, Ti within a range from 92 mol % to 99.96 mol %, W within a range from 0.04 mol % to 8 mol %).
As for catalytic poison of the organohalogen compounds, fluorine compounds have larger influence than chlorine compounds. Accordingly, a catalyst which has a high activity to the organohalogen compounds containing not only chlorine, but also fluorine, bromine, and the like, is required. Further, the catalyst having a continuity in its activity is desired.